Despite economic challenges, Walmart is staying ahead of the curve. The retail giant released its impressive first-quarter earnings report on Friday, which showed growth across the board. Total revenue was equal to $161.5 billion, a 6 percent increase from its performance in the first quarter last year. Walmart also saw its net sales and adjusted operating income increase by 5.9 percent and 13.7 percent, respectively. Barron’s also reported that increased purchases by wealthy shoppers and an increase in e-commerce sales are also driving Walmart’s sales up. The company reported that global e-co…